Greenhouse heaters

[Stefanie]

I am finally getting around to getting an estimate to run a natural gas line to my two greenhouses.. one is 10x20 glass attached to the house, and the other is 8x14 twin wall poly free standing.

I think it's going to cost a fortune just to get the line run, so I'm trying to be slightly economical about the heaters themselves (the point is to not have it cost a fortune each month to heat the greenhouses!). A friend, who also grows orchids, has ProCom brand.. these are vent free 99% blue flame heaters, and he says he has no problems with bud blast. The only thing I don't like about them, is that they have no real thermostat... apparently they are adjustable, but for example, night and day differentiation must be done manually.

They are also nice because they are relatively small, and my greenhouses are small. My other choice is Empire, but they are huge and will require venting, as well as reconfiguration of the greenhouse wall...

anyone out there using ProCom heaters to heat their greenhouse, and if so, what's your opinion? thanks

[Oscarman]

Wish I had 1 greenhouse....nevermind 2!

It seems to me that temperature control is the main concern with a greenhouse (in conjunction with ventilation and air movement). Of all the greenhouse equipment, I would get the best unit possible, with all the features desired - regardless of cost. Thermostat adjustment/control would be a mandatory feature.

#1) Dependability
#2) Clean burning
#3) Temperature control
#4) Energy efficiency

Don't you want to spend your time on the plants and their care, not monkeying with temperatures?

[Ray]

I agree...the heater is the LAST thing to go cheap with!

1) Have you sized the heaters properly? I would speculate that they will need different outputs, based upon the GH sizes, configurations and coverings. (There is a sizing calculator at my website.)

2) Unvented is fine as long as it is burning cleanly, which no gas heater will do forever. Once the burner gets even the slightest bit sooty, or a spider spins a web somewhere inappropriate in the summer, it will burn the fuel incompletely and emit ethylene. If the GH is nice and tight, it will affect the plants, and it can actually be toxic to the plants, not just cause bud blast.

3) Forget varying the day- and nighttime temperatures. The best strategy is to set the thermostat for a minimum temperature and let nature run its course from there. Artificially heating a GH on a gray day can lead to weak, leggy growth. If the sun is bright, it will heat the place AND provide the energy source the plants need.

[Stefanie]

Thanks Dave & Ray - I guess I view this as going from Kerosene, to something that has to burn more cleanly, and will be much easier to manage. If I thought the ProCom would not be efficient or functional, then I would definitely go with the Empire, but the size is quite a factor. The Empire heaters are big and heavy, and will require professional installation, as well as some serious greenhouse wall deconstruction. I would also loose an entire bench in the little greenhouse, due to the 3 foot verticle clearance required. With the ProCom, they are small enough that I can put the 20,000 BTU one in the isle, and will ask the plumber to make a disconnect, so I can remove it in the summer!

I have calibrated the BTUs, and am oversizing a bit.. 30,000 for the 10x20 attached, and 20,000 for the free standing. This is with an estimate temp of 58. I have in the past frequently let both greenhouses get into the 40s, so I think that these values will be sufficient in all but the most bitter weather, and then there is always the kerosene as backup!

I wish Empire made a smaller electric free heater, but they don't, so I guess I'll give the ProCom a try and see what happens. They HAVE to be better than Kerosene, which I've used for the past 6 years...

stef